(1) Field of the Invention
The present invention relates to a telephone terminal that performs a voice call by inputting/outputting voice based on audio signals transmitted through a telephone line network from a transmitter/receiver.
(2) Background Art
These days Internet terminals allowing data communication through Internet networks are becoming widespread. Such Internet terminals function to perform a voice call (hereinafter referred to as the “Internet call function”) by inputting/outputting audio signals from/to an Internet network and inputting/outputting a voice based on the audio signals from/to a transmitter/receiver apparatus connnected to the Internet terminal (e.g. a headset: an apparatus with a microphone integrated into a headphone or an earphone).
In such an Internet terminal, voice based on the audio signals input/output from/to the Internet network may be output/input from a speaker and a microphone provided in the Internet terminal. However, depending on the location of the speaker and the microphone, the voice output from the speaker may be difficult to be heard or the volume of the voice input from the microphone may be low, so that a voice call in good condition cannot be obtained in some cases. Therefore, it is usual to use the transmitter/receiver apparatus connected to the Internet terminal to perform a voice call by the Internet call function.
However, the transmitter/receiver apparatus, which is a dedicated apparatus to be used for performing a voice call by the Internet call function, cannot be used for other purposes.
It is preferable that an apparatus to be used for other purposes can also be used as an apparatus for the Internet call function. Therefore, an apparatus dedicated to performing a voice call by the Internet call function is then no longer necessary.
An example of the apparatus to be used for the Internet call function is a known telephone terminal that performs a voice call by inputting/outputting voice based on audio signals transmitted through the telephone line network from a transmitter/receiver. Such a telephone terminal can be used as an ordinary telephone terminal when the Internet call function is not used.
Specifically, a telephone terminal that includes a telephone connection unit for connecting a line to the other party's telephone terminal as a telephone terminal on the other end of the line through a telephone line network. The telephone terminal is capable of performing a voice call with the other party's telephone terminal by inputting from a transmitter/receiver audio to be transmitted as audio signals to the other party's telephone terminal connected by the connection unit through the telephone line network and outputting from the transmitter/receiver audio based on audio signals transmitted from the other party's telephone terminal. The telephone terminal may also comprise an audio input/output unit that is provided in addition to the telephone connection unit and that is capable of inputting/outputting audio signals from/to an outside source through an Internet network. The telephone terminal may also comprise a switch unit for switching an output destination of audio signals based on audio input from the transmitter/receiver and an input source of audio signals to be output as audio from the transmitter/receiver between the telephone line network and the audio input/output unit according to an operation of a user.
In the telephone terminal constituted as above, the output destination of audio signals based on audio input from the transmitter/receiver and the input source of audio signals to be output as audio from the transmitter/receiver may be switched to the audio input/output unit capable of inputting/outputting audio signals from/to an outside source. Once the output destination and input source of audio signals are switched to the audio input/output unit, audio based on audio signals input from the outside source through the audio input/output unit is output from the transmitter/receiver, and audio signals based on audio input from the transmitter/receiver are output to the outside source through the audio input/output unit. Accordingly, by connecting the present telephone terminal to an Internet terminal having a function to perform a voice call (hereinafter referred to as the “Internet call function”) based on audio signals input/output from/to an Internet network, a voice call by the Internet call function may be performed indirectly by using the transmitter/receiver of the present telephone terminal.
In terms of a communication charge for a voice call these days, it is usually less expensive to perform a voice call by the Internet call function through an Internet network than to perform a voice call through a telephone line network. Therefore, users who want to enjoy a voice call for a long time may prefer to perform a voice call by the Internet call function. To perform a voice call by the Internet call function indirectly by using the above described telephone terminal, it is necessary to make preparations in advance on the Internet terminal side in order to make a voice call by the Internet call function, since the telephone terminal cannot control the operation of the Internet terminal. “To make preparations” here means to perform an operation of starting the Internet terminal and an operation for starting use of the Internet call function and a voice call.
To perform a voice call by the Internet call function indirectly by using the telephone terminal, a user first performs voice call through the telephone line network by using the telephone terminal. Then, the user informs the other party that a voice call by the Internet call function will be performed if the Internet call function is available to the other party. “The Internet call function is available” means, for example, a state in which the other party has (or uses) a computer system or a telephone terminal having a function to achieve the Internet call function and can use the Internet call function normally.
Once both the user and the other party have completed preparation for performing a voice call using the Internet call function, the output destination and input source of audio signals are switched to the audio input/output unit. By disconnecting the line through the telephone line network the output destination and input source of audio signals are switched to the audio input/output unit, it will be possible to prevent the communication charge from increasing unnecessarily as time goes on due to the still connected line despite the already terminated voice call through the telephone line network (In Publication of Japanese Unexamined Patent Application No. 10-155034, page 9, paragraph [0074], the following description is included: Once a call through the Internet telephone is started as above, the calling side Internet telephone set 1a disconnects the connection through the ordinary telephone (S14a), and the call through the Internet telephone is continued afterward.).
However, it is preferable that the line to the other party's telephone terminal connected through the telephone line network remains connected for a while even after the output destination and input source of audio signals are switched to the audio input/output unit. This enables the output destination and input source of audio signals to be switched back to the telephone line network and confirm the status of the other end, if the voice of the other end cannot be heard after the output destination and input source of audio signals are switched to the audio input/output unit.
Then, it is possible to switch the output destination and input source of audio signals to the audio input/output unit again after confirming that the other end has completed preparation, or to choose to continue or stop the voice call through the telephone line network if the Internet call function is unavailable to the other end.
An object of the present invention is to provide a telephone terminal and a call system in which the line to the other party's telephone terminal connected through the telephone line network remains connected for a while even after the output destination and input source of audio signals are switched to the audio input/output unit as well as a terminal control program to be used in the telephone terminal and the call system.